Post by jimbo on Mar 22, 2021 10:20:22 GMT
The March Underground News has an article on the history of tripcocks on trains. I have never really understood the importance of the tripcock at the rear of trains, which risks a train becoming back-tripped and brought to a halt. The tripcock hangs from the front right corner of a train, and will halt a train that attempts to pass a signal at danger by striking the train-stop linked to that signal. Since trains can work in either direction, there is a similar tripcock at the diagonally opposite position on the other end of the train.
It seemed to me that the tripcock at the rear of a train was just a nuisance, and should not be able to halt a train. This seems to have been the policy adopted by the designers of 1972TS, who adapted the design of the first Victoria line trains to run under conventional signalling. However, when procedures for dealing with failures were documented, a major weakness was revealed. If a driver was unable to drive from the leading cab, they went to the rear cab to drive in reverse. A lookout was appointed to ride in the leading cab and report by train phone to the driver at the rear. This lookout might be the train guard, or a co-opted member of station staff, but in any case someone less familiar with the layout of the line and signals than a regular driver. At such a time the driver operating from the rear cab had an operating but pointless tripcock, whilst the leading cab was not the driving position and therefore had no tripcock protection! I believe this was subsequently corrected, and no further train orders followed this principle.
However, many years back in the lead up to the evening peak we found that trains were being back-tripped entering Marble Arch westbound platform. To minimise delays it was decided to advise train guards on 1962TS to cut-out the rear trip at Bond Street, and then reset the trip and cut it back in at Lancaster Gate. I queried why we didn't leave resetting the trip and cutting it back in until the train reached its destination. Resetting and cutting in over a tube station pitted road is not easy and added to the delay of each train. I thought it better to use reversal time at the end of the trip, but I was told that we were not allowed to run trains with the rear trip cut out. Was that true back then, and is it still true?
It seemed to me that the tripcock at the rear of a train was just a nuisance, and should not be able to halt a train. This seems to have been the policy adopted by the designers of 1972TS, who adapted the design of the first Victoria line trains to run under conventional signalling. However, when procedures for dealing with failures were documented, a major weakness was revealed. If a driver was unable to drive from the leading cab, they went to the rear cab to drive in reverse. A lookout was appointed to ride in the leading cab and report by train phone to the driver at the rear. This lookout might be the train guard, or a co-opted member of station staff, but in any case someone less familiar with the layout of the line and signals than a regular driver. At such a time the driver operating from the rear cab had an operating but pointless tripcock, whilst the leading cab was not the driving position and therefore had no tripcock protection! I believe this was subsequently corrected, and no further train orders followed this principle.
However, many years back in the lead up to the evening peak we found that trains were being back-tripped entering Marble Arch westbound platform. To minimise delays it was decided to advise train guards on 1962TS to cut-out the rear trip at Bond Street, and then reset the trip and cut it back in at Lancaster Gate. I queried why we didn't leave resetting the trip and cutting it back in until the train reached its destination. Resetting and cutting in over a tube station pitted road is not easy and added to the delay of each train. I thought it better to use reversal time at the end of the trip, but I was told that we were not allowed to run trains with the rear trip cut out. Was that true back then, and is it still true?
